When creating a book containing many images such as cartoons, it is necessary to use a technique different from a technique of creating a book containing many characters. For this reason, techniques of supporting the creation of cartoons have been developed (for example, Japanese Patent Laid-Open Nos. 2013-089198, 2000-194671, H10-105683, and 2005-038164). These techniques include techniques effective in creating electronic books.
When cartoon books as general books are to be sold in the form of electronic books, some books are converted into electronic books without changing the layout of the contents of the cartoon books. In such a case, however, some books are very difficult to read depending on the situation in which they are browsed. When browsing electronic books, for example, general users often use portable devices such as smartphones. Such portable devices have smaller display sizes than personal computers. For this reason, electronic books displayed on the displays of portable devices are sometimes difficult to read because of characters being too small.
Under the circumstances, various contrivances have been studied to facilitate browsing. For example, the size of one page may be reduced to make it correspond to the area that can be displayed on a display. In such a case, the number of pages increases. As a result, a technique is required which supports the creation of an electronic book containing many pages containing images.